Unfortunately this doesn't seem to be a consideration to manufacturers. Even if they are meant to work offline, this is going to be the least-tested path. IIRC

Unfortunately this doesn't seem to be a consideration to manufacturers. Even if they are meant to work offline, this is going to be the least-tested path. IIRC there have been cases with certain internet-enabled thermostats failing to do the core thing (regulate the temperature) because they couldn't phone home. The solution if you want something without such surprises is to work with open or semi-open devices (e.g. can be controlled by your own home automation server) that don't just magically connect to the internet and just work. The problem with this is that using your own home automation server requires a degree of knowledge not readily found in the population at large, and can in many cases give even more control to the partner who installed it over an internet-of-things solution. It does seem to me that a lot of home automation devices are marketed as being about being able control things that were operated by a switch by a remote control that can work from another country, rather than about better regulating light or heat or security. Perhaps some people see such tools as they are marketed as a way to gain power over others.